This invention concerns a hinge to connect the legs and frame of a pair of spectacles.
The connecting hinge according to the invention enables the frame of the spectacles, or the part holding the lenses, to be resiliently connected to the relative legs.
The invention can be fitted to any type of sunglasses or spectacles to assist the eyesight and can be adapted substantially to any frame advantageously, but not only, of a type including non-metallic components such as horn, tortoise-shell, artificial or synthetic materials or compounds of a resinous nature.
Very many types of hinges to connect the frame and legs of spectacles are disclosed in the state of the art and make possible a given determined spreading apart of the legs beyond their normal open position of use.
The state of the art commonly discloses the use of hinges provided with at least one cam element having a suitable profile able to cooperate with an at least partly spherical element movably guided inside a cylindrical seating made within the leg itself.
The movement of the spherical element within the cylindrical seating is resiliently resisted, for instance, by a spring lodged at the rear within the cylindrical seating.
This spherical element may consist of a metallic ball directly resisted by the spring or of a metallic cylinder having a hemispherical end, as disclosed in FR-A-2.026.893.
EP-B-0006075 discloses an embodiment in which the sphere is not directly opposed by the spring, but an element is interposed which has the form of a second sphere or flat element to reduce friction between the sphere and the spring and to assist the sliding of the sphere within the cylindrical seating.
The limits of maximum spreading apart of the legs are generally applied by actions of direct opposition between the spherical element and a part of the cam, with the resulting occurrence of localised stresses at a short distance from the pivoting axis and in severely oblique directions.
FR-A-2.026.893 discloses a hinge in which the pivoting axis is embodied with a pivot that connects with a hinged joint two metallic elements solidly connected to the frame and relative leg respectively.
The resilient system of stabilisation and positioning of the legs consists of cooperation between a profiled cam solidly fixed to the frame and a metallic sphere acting as a tappet in relation to the profile of the cam itself and movably guided within a cylindrical seating provided within the metallic element solidly fixed to the leg.
The maximum limit of spreading apart of the legs is provided by an action of abutment between a step made on the profile of the cam and the end of a prolongation of the metallic component of the leg.
The known embodiments entail some shortcomings. The use of a spherical element as an element to cooperate with the cam generates stresses of a punctuate type. These stresses are concentrated at the point where the spherical element comes into contact with substantially flat surfaces forming the profile of the cam.
This entails the need to use especially strong material to form the cam so as to prevent punctuate wear and deformations on the profile of the cam.
Moreover, the abutment elements which limit the maximum spreading apart of the legs are in an outer position and, as time goes by, lead to a deterioration of the aesthetic appearance and to possible functional damage.